[llvm-dev] Reserve registers not to be used by the compiler

Matt Arsenault via llvm-dev llvm-dev at lists.llvm.org
Mon Dec 21 17:02:46 PST 2015

On 12/21/2015 07:40 PM, Rail Shafigulin via llvm-dev wrote:
> Does anyone know if there is a way to reserve a register set not to be 
> used by a compiler? For example there are 64 available registers and 
> the compiler can use only registers 0-31 and 40-45, and the others 
> should be left alone.
> I know that the simplest solution is to simply change number registers 
> in one of the .td files, but what I'm looking is an option to use at 
> run time. I need this to research various register combinations. 
> Recompiling and running tests takes some time. If I could compile my 
> code with say 128 registers and thn tell compiler to use only a 
> certain set (say 0-32) at run time then this would significantly speed 
> up my testing. I would be able to see what the code is doing for the 
> same test with a 32 registers vs 64 vs 96 vs any number up to 128.
> Does anyone know if there is a way to do it? Any help is appreciated.
> -- 
> Rail Shafigulin
> Software Engineer
> Esencia Technologies
> _______________________________________________
> LLVM Developers mailing list
> llvm-dev at lists.llvm.org
> http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
You can override TargetRegisterInfo::getReservedRegs and reserve any 
registers you do not want allocated.

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